I was 12 years old, sitting in school three blocks away from the World Trade Center on September 11, 2001, when the planes hit the twin towers and changed the way I understood the world around me forever. I will never forget what I witnessed that day: people covered in debris, surrounded by piercing, blood-curdling screams and cries. I will never forget the terrifying hour we spent trying to get home, a route that was normally a ten-minute walk from school, only to find that our neighborhood — also a few blocks from ground zero — looked like a war zone.

The next years of my life were spent coming of age with undiagnosed symptoms of Post Traumatic Stress Disorder that turned my teenage life into a nightmare. Part of my recovery was learning to see the good with the bad, because the truth is the world is pretty horrific at times, but it can be pretty awesome, too.

Last year, I wrote a book about my experience, and as a result, have received emails from children across the country asking me about 9/11 and PTSD. Here’s a sampling of their questions, along with my responses.

Helania Hovitz

Helaina Hovitz, 12, one week before September 11, 2001

What was it like in your neighborhood in the days right after 9/11?

We had more threats of collapsing buildings, bomb scares on nearby landmarks, and instructions to pack an emergency bag and have the whole family ready to leave on a split-second's notice—without having any idea where we would go. The National Guard showed up, the sound of a plane sent me into a hysterical panic, I wasn't sleeping, I was always worried, paranoid, ready to take off at the next attack, having nightmares and flashbacks, feeling like a sitting duck waiting to die. The rest of the world resumed "life as normal," but everything had stopped in our neighborhood, which was basically treated as a war zone.

What made you want to write a book about 9/11?

I decided to start writing about it because my reaction to the terror was very severe and lasted for a very long time. When I got better, I realized there are many children and teenagers in this country who live with PTSD, which is a long-term reaction to terror and other bad things that sometimes happen.

How long did the haze from the smoke in Manhattan stay?

The haze stayed in our neighborhood for a very, very long time. Six months later, there was still some debris in the air. The air quality was very dangerous for a long time, but many people didn't leave because they didn't have anywhere else to go.

Do you ever go back to that day and wonder why it happened?

I think about that day all the time, and we do in fact know why, to some extent, the people behind the attacks did what they did. But that doesn't make it any less sad or scary. Sometimes bad things happen and we will never really know why they do, but the most important thing is to try to be as strong as we can be, and be good people in the world to try to make it a better place.

Was it hard for you to understand what was going on at that time or did you understand what was happening right away?

It was very hard for me to understand what happened at that time, not just with the attacks, but what was happening to me on the inside as a result of PTSD, and the way I experienced life after that. If something makes you feel sad, that's OK. We can be brave and still feel sad. What's important is that we try to be good people in the world ourselves, and that is something that is always in our control when so much around us feels out of control.

Have you ever felt mistrust for Muslims because of the attack?

Right after the attacks, kids were constantly being told who the bad guys were and what they looked like, and to be on the lookout for people who looked like them, along with any suspicious activity. New York City has always been a very diverse place. As a child, it was almost like watching a cartoon and being told who the villain is — and that the villain could be anywhere, like on the subway holding a backpack or in a crowded store. But fortunately, I had a wonderful teacher in our school who taught us early on that one small group of people do not represent an entire race or religion, and that these people who chose to do something horrible were not doing it in the name of any or all of them. People of all races, ages, religions, and walks of life have the ability to do bad things, and good things, too.

Helania Hovitz

Helaina Hovitz today, in front of a local school in her downtown neighborhood.

How did you put the past behind you? Or did you?

I had a teacher in college who told me that while our past can be painful, we have to take what we can from it and remember what’s important in order to live more happily in the present. For example, if you broke your arm climbing a giant tree, or burned yourself touching a hot stove, you’d want to remember that next time so you could decide whether to do it again. In this case, something bad happened to us that we could not control, and that’s what made it so hard to put behind us. But through support and therapy, I did learn to take what would help me from my past and cope with all of the horrible parts in order to live a life where I felt safe again, or as safe as I could.

How did 9/11 change your perspective on life and the way you see people?

Part of my recovery was learning to see the good with the bad, because the truth is the world is pretty horrific at times, but it can be pretty awesome, too. With effort and the right tools, I learned to see the good in awful situations.

Do you ever worry that something like 9/11 could happen again in NYC?

I think part of me has worried about that every day for the past 16 years. What I have learned, though, is that you can’t spend every day worrying about something that might happen, and watching the news or listening to people talk about new threats of something like that can make it really hard to hang on to that feeling of feeling safe and not worried. There have been attempts, a couple of them successful, in NYC and unfortunately around the world, to do something like 9/11 again. All we can do about it is be sure to reach out to help people or offer a kind word when it does, and focus on loving the people who are important to us as much as we can every day.

Helaina Hovitz is an editor, writer, and author of the memoir After 9/11. She has written for The New York Times, Salon, Glamour, Forbes, Women's Health, VICE, and others. She is currently the editor of content collaborations at Upworthy/GOOD. Twitter: @HelainaHovitz, www.HelainaHovitz.com and Facebook.com/HelainaNHovitz